1. Field of the Invention
This invention relates to an improvement in plain bearings.
2. Prior Art
Difficulties arise in providing adequate bearings where heavy loads, including impact loads, must be accommodated in environments that are hostile to lubrication and to the bearing materials, such as wet, dirty, environments. The problem is further accentuated if maintenance is likely to be neglected. This type of situation exists, for example, in the wet environment in which certain machinery is used in steel mills. In particular, a need exists for improved wheel bearings used with work roll chocks of steel finishing mills and roughing mills. Work roll chocks are heavy roll supports on movable trucks that have track-guided wheels. The trucks permit moving the work rolls into and out of a roll stand, and the supporting wheels are subjected not only to heavy loads, but also the dirt, dust and water of the surroundings. A need also exists for improved bearings for conveyor wheels used in industrial environments with heavy loads and at low rotational speeds. In these types of applications, particularly with wheels for supporting work roll chocks and conveyors, roller type bearings were found to fail very rapidly from the lack of lubrication, presence of water or moisture, and the impact loads to which the bearings were subjected, as when a crane lowers a work roll chock onto guide tracks.
Accordingly, a definite need exists for a strong bearing of inherently low friction, which will function with little or no lubrication, and which is corrosion resistant to withstand a wet environment.
Hardened steel plain bearings have been recognized as satisfactory under heavy loads at low rotational speeds, but they have been unable to function without failure under such adverse conditions as outlined above. The same is also true of bronze bearings, stainless steel, and carburized alloy steel bearings, all of which have been tried with wheel and axle combinations for steel mill work roll chocks, but have suffered early failure.